Method of making decorative panels of stone material or the like

ABSTRACT

A pack (P) of slabs is formed by positioning successive layers of ornamental slabs of stone alternating with supplementary layers of slabs in succession on a support base ( 10 ). A liquid-tight container (C) is then formed around the pack (P) with a peripheral space left around the edges of the layers. The container (C) is then subjected to a vacuum and a settable fluid binder is introduced into the container that the binder fills the whole of the peripheral space, penetrates the gaps between the slabs, and covers the pack of slabs. The vacuum is then released and the binder is permitted to set to produce a consolidated pack of slabs in a block in which the faces of the block corresponding to the edges of the layers are covered by a hermetic covering of binder. The block is then cut to produce composite panels.

The present invention refers to a method of making decorative panelscomprising slabs of stone material or the like, for instance marble orgranite.

Known methods show that, to this purpose, on a basis support a stack orpackage of layers is formed, said layers consisting of parallel slabs ofthe decorative stone material, and of additional layers, such asframework or reinforcement layers and separating layers between thepanels. Then the package is placed inside a liquid-tight formwork, and adepression is therein created and maintained while feeding a hardenablefluid binder intended for encapsulating the stack and for penetratinginto interstices among slabs, consolidating possible fractures of theslabs themselves. Afterwards, the binder is made to harden so to obtaina monolithic block that is cut to produce panels comprising at least onedecorative slab joined to at least one framework layer.

Examples of these methods are disclosed in WO-A 91/08093 and in theItalian patent application No. TO92A000988. WO-A 91/08093 furthersuggests to insert, between one head of the stack and the adjacent wallof the formwork, a bin-shaped filling element in order to fill the emptyspace left by a stack formed with slabs of length smaller than theformwork. This prevents wastes of quite expensive binder.

The known method has a certain number of disadvantages.

The stack must be formed with equal slabs, and this is not easilyobtainable due to the different sizes of the raw blocks, or a trim isrequired, which makes costs increase.

Moreover, a series of different filling elements must be provided so tobe adapted to different lengths stacks, and this makes costs increasetoo. As the number of different filling elements will be obviouslylimited, an exact compensation will be rarely possible and there will beoften need to fill the remaining empty spaces with the quite expensivebinder.

Furthermore, it is difficult to obtain in the formwork vacuum conditionssuch as to allow the penetration of the binder all over the block, dueto the presence of both humidity and gaseous residuals generated by thebinder.

Finally, the raw panels obtained after cutting have a reinforcementlayer on one side only of the stone material slab: so it isautomatically identified the side to be polished (that withoutreinforcement), and this implies the impossibility to produce slabs withdifferent superficial treatments, such as open-stain or continuous-veinslabs.

As it is known, actually, by cutting a thick slab in half, theopen-stain are the two internal sides, the continuous-vein are insteadthe internal side of a slab and the external side of the other one, theaesthetic result being of course very different.

According to the invention a method is instead provided that overcomesthe drawbacks of the known prior art.

These and other objects of the present invention are achieved with themethod defined in the following claims.

For better explanation reference is made to the attached drawings, inwhich:

FIG. 1 is a schematic elevation view showing the formation of a stack ofslabs;

FIG. 2 is a sectional partial view, scaled up, of the stack of FIG. 1;

FIG. 3 is a vertical section schematic view of a formwork in which thebinder casting takes place;

FIG. 4 is a schematic view from the above of a stack portion impregnatedwith binder;

FIG. 5 is a vertical section schematic view showing the cutting step ofa lateral side of the stack of FIG. 4; and

FIG. 6 is a vertical section schematic view of a raw panel.

With reference to FIGS. 1 and 2, numeral 1 denotes a stack ofsuperimposed layers comprising slabs 2 of the decorative material, forinstance marble, granite, etc., alternated with additional layers 3, 4.If slabs 2 in stack 1 have different sizes, it is possible, alreadyduring the stack formation, to make a compensation of the sizedifferences by arranging along one or more edges of the smaller slabselements 20A of stiff material, for instance pieces of the same slabs 2material. These additions will be kept in position, in this step, by theweight of the overlaying slabs.

An alternative way of carrying out such compensation will be describedlater on.

Layers 3 are framework sheets or thin slabs, while layers 4 areseparating or detaching layers between the single panels and theyconsist of sheets or thin slabs too or of a fluid layer.

As also disclosed in WO-A 91/08093, stack 1 is formed on a supportstructure 5, capable of supporting, all their extension long, slabs ofcommercially used maximum sizes (for instance about 3.50 m×1.55 m).Support 5 can comprise only a horizontal basis, as in FIG. 1, or thebasis and a longitudinal vertical wall. The second solution is usefulfor forming a stack 1 with vertical slabs or for vertically arranging astack such as that of FIG. 1 before feeding a fluid binder inside a castcontainer. Slabs 2 are stacked by using for instance a travelling cranesystem having a frame 6 vertically movable and equipped with suctioncaps 7, while the additional layers 3 and 4 car be applied by hand.

Each slab 2 is in contact, on both its main sides, with a reinforcementlayer 3, and each of the two reinforcement layers 3 associated to a slab2 is in contact with a separating layer 4. Preferably, the reinforcementlayers 3 have such a structure to allow the passage of the fluid binder(for instance a synthetic resin hardenable at room temperature),intended for impregnating and encapsulating stack 1. Layers 3 have forinstance a net structure. Thanks to the presence of layers 3 on bothsides of each slab 2, the binder effectively penetrates all over stack1, entirely consolidating possible fractures in slabs 2.

Separating layers 4 are made of a material that does not adhere to thebinder, so to make the separation of adjacent panels easy.

Further features about the structure and the materials of layers 3 and 4are contained in said prior documents, to which reference is made.

With reference to FIGS. 3 and 4, around stack 1 a liquid-tight sturdymetallic formwork 10 is formed that, in the shown embodiment, works alsoas an autoclave for the impregnation of stack 1 with the fluid binder.Formwork 10 is constructed by joining the necessary lateral walls 8 tosupport 5 and by adding a closing lid 9. Not shown gaskets Guarantee thetightness. Some room for the passage of the binder must be left betweenthe sides of stack 1 and the walls of framework 10, and to this purposespacing elements, not shown, can be employed. If the stack sizes do notcorrespond to those of the formwork 10 (except the aforesaid space),filling elements 21, which will be described later on, are providedbetween lateral walls 8 and stack 1. Formwork 10 is constructed afterhaving arranged stack 1 with the layers being substantially vertical.

Formwork 10 can also form a simple cast container, open on one side,that will be further inserted into a suitable autoclave.

Before feeding the binder, possible differences among the sizes of slabs2 are compensated, in case these differences have not already beencompensated during the formation of stack 1.

To this purpose, a high density (higher than the one of the bindingmaterial) expandable material, for instance polyurethane, is introducedinto formwork 10. This material is fed at the liquid state through oneor more ducts 11 and it is made or let to expand so to fill the emptyspaces left from small size slabs 2. Due to the high density, theexpandable material remains confined near the edges of slabs 2, and itdoes not penetrate into the spaces between the various layers of stack1. The presence of an expanded material on the periphery of the layersadjacent to the involved slab is not important, since such material willbe removed with cutting.

The same material can be employed to form, at least partially, thefilling elements 21 necessary to bring stack 1 in contact with the wallsof formwork 10. In this case, the filling elements formation will takeplace simultaneously to the size differences compensation of the slabs:practically, one or more filling elements 21 will have protrudingportions that join the involved slabs, as shown in 20B in FIG. 4.

The expanded and solidified material of these elements 21 can be alsorecovered after the panels separation and reused for an approximateadaptation between the sizes of stack 1 and formwork 10. Then liquidmaterial will be added to compensate the remaining differences. Thesolid filling elements 21 can be mounted in the formwork beforeintroducing stack 1.

In a variant, the filling elements 21 are made of air cushions: thesecan be introduced too in formwork 10 before stack 1.

Fluid binder 15 feeding takes place after that a depression has beencreated in formwork 10, by evacuating air through one or more ducts 12.During air evacuation from formwork 10, stack 1 is advantageously heatedso that the possible humidity still present upon reaching the vacuumcondition evaporates. Moreover, formwork 10 can be associated to afreezing system (not shown) for the humidity evaporated in consequenceof heating. This way the remaining humidity is made unimportant for thecycle.

Binder 15 is fed from the top, through a duct 13 provided in lid 9, orfrom the bottom to facilitate the evacuation of the remaining air. It isspread out into all the interstices among the single components of stack1, around stack 1 and below it, also completely or partially wrappingthe filling elements 21. Penetration inside stack 1 is facilitated bythe presence of the reticular reinforcement layers 3 on both sides ofeach slab. Binder feeding ends when all stack 1 is covered by a liquidbinder head of a few centimetres.

Binder 15 is degassed while is fed in the formwork, so to reduce thegeneration of gaseous residuals. In order to help to create vacuumconditions, a washing of formwork 10 with inert gases is also preferablycarried out, said washing allowing to eliminate humidity residuals.

Upon termination of the binder feeding, the inside of formwork 10 isbrought to a pressure higher than the atmospheric pressure so to createa piston effect that facilitates the hardening. Once the binder ishardened, a monolithic block is obtained in which hardened binder 15wraps stack 1, consolidating possible deposits 20A for adapting sizesfor single slabs 2, and wrapping or joining filling elements 21 to stack1, as visible in FIG. 4. In this figure are visible a slab 2A having anaddition 20A obtained during the formation of stack 1, and a slab 2Bhaving an addition 20B obtained from the expandable material andintegrated with a filling element 21.

The monolithic block is taken out from formwork 10 and it is brought toa cutting station, where cutting preferably takes place according to themodes disclosed in the Italian patent application No. TO92A000988. Inother words, and as visible in FIG. 5, block 16 is cut, on all thelateral sides, perpendicularly to slabs 2 extension plane, so to removenot only the layer of hardened binder 15, but also possible layers ofexpanded material and solid filling elements 21 and an edge portion 22of stack 1 layers. This way separating layers 4 not adhering to thebinder are exposed to air and an easy separation of the panels isallowed, as disclosed in said Italian patent application.

As said, solidified filling elements 21 can then be reused.

In FIG. 6 a raw panel is shown obtained by block 16. Panel 25 has areinforcement layer 3 on both sides. One of such layers shall beobviously removed in the following polishing step. Nevertheless, thefact of being able to choose the side to be polished causes thepossibility to choose among different kinds of superficial polishing,for instance in order to obtain open-stain or continuous-vein slabs.

It is evident that what has been disclosed is given as a non limitingexample and that variants and modifications are possible without goingout the protective scope of the invention.

1-17. (canceled)
 18. A method of making decorative panels of stonematerial or the like, wherein: a stack is formed comprising parallelslabs of the decorative stone material and of additional layers,comprising framework layers and separating layers between panels; thestack is placed inside a liquid-tight container, interposing fillingelements at least between one head of the stack and one wall of thecontainer if the stack has a length smaller than the container; adepression is created in the container, said depression being maintainedwhile feeding a hardenable binder, intended for impregnating andencapsulating the stack, the binder being of a material that does notadhere to the separating layers; the binder is let or made to harden soto obtain a monolithic block that is then cut to produce raw panelscomprising at least one decorative slab joined to at least one frameworklayer; wherein possible size differences among slabs in the stack arecompensated; filling elements are also introduced or formed in thecontainer in order to fill empty spaces left from a stack having alength smaller than the container; and, as filling elements, expandableelements are at least partially employed.
 19. The method according toclaim 18, wherein, in order to compensate said size differences amongslabs, onto one or more edges of small size slabs, additions of highdensity expandable material are made that fill the recesses existing onthe sides of the stack in correspondence to said small size slabs. 20.The method according to claim 19, wherein said high density expandablematerial is fed in the container at the liquid state and it is let ormade to expand before feeding the binder.
 21. The method according toclaim 18, wherein, in order to compensate said differences among theslabs sizes, during the stack formation, along one or more edges ofsmall size slabs, stiff elements are arranged, capable of being joinedby the binder to the respective slabs.
 22. The method according to claim21, wherein said stiff elements comprise elements made of the same slabsmaterial.
 23. The method according to claim 18, wherein said fillingelements comprise elements of high density expandable material fed inthe container at the liquid state and made or let to expand beforefeeding the binder.
 24. The method according to claim 19, wherein saidfilling elements are elements of high density expandable material fed inthe container at the liquid state and made or let to expand beforefeeding the binder.
 25. The method according to claim 24, wherein saidfilling elements are made of the same expandable material used for saidadditions, and are formed simultaneously thereto.
 26. The methodaccording to claim 23, wherein, in order to make said filling elements,solid elements are employed obtained by expanding said expandablematerial and recovered after cutting, said elements providing for anapproximate adaptation between the sizes of the stack and the container,liquid expandable material being added to said elements so to fill theremaining empty spaces.
 27. The method according to claim 19, whereinsaid high density expandable material is polyurethane.
 28. The methodaccording to claim 24, wherein said high density expandable material ispolyurethane.
 29. The method according to claim 18, wherein said fillingelements comprise air cushions.
 30. The method according to claim 18,wherein, during the stack formation, a framework layer is applied ontoeach of the main sides of each slab of stone material, each frameworklayer being associated to a separating layer and the cutting operationproducing raw panels comprising a decorative slab provided with aframework layer on both sides.
 31. The method according to claim 18,wherein, while creating the depression in the container and feeding thebinder, the stack is heated so to be brought up to a temperature such asto allow, upon reaching the wanted vacuum conditions, the humiditypresent in the stack to evaporate.
 32. The method according to claim 31,wherein the water vapour originating from the evaporation is made tofreeze.
 33. The method according to claim 31, wherein, duringimpregnation, a washing of the container with inert gases is carried outin order to eliminate any humidity residual.
 34. The method according toclaim 31, wherein the binder is made to harden by applying a pressurehigher than the atmospheric pressure.
 35. The method according to claim34, wherein, upon termination of the binder consolidation, the block iscut along planes perpendicular to the layers, up to a depth such as toremove the solidified binder, the possible filling elements and the edgeportions of the layers.
 36. A decorative panel comprising at least adecorative slab of stone material or the like joined to at least oneframework layer, obtained through a method according to claim 18.